초록 ▼

A method for use in processing an analog signal from a laser scanning bar code reader containing information representative of reflected light from indicia including regions of different light reflectivity, and including narrow and wide elements of the same reflectivity of the indicia, by locating e

A method for use in processing an analog signal from a laser scanning bar code reader containing information representative of reflected light from indicia including regions of different light reflectivity, and including narrow and wide elements of the same reflectivity of the indicia, by locating edge transitions between narrow and wide elements; estimating the edge shift associated with such transitions; and changing the edge position to correct for convolution distortion.

대표청구항 ▼

1. A method of correcting for convolution distortion in a laser scanner for sweeping a bar code symbol having elements of wide and narrow widths separated by edges and arranged along a scan direction with an oversized laser beam spot having a spot width, as considered along the scan direction, which

1. A method of correcting for convolution distortion in a laser scanner for sweeping a bar code symbol having elements of wide and narrow widths separated by edges and arranged along a scan direction with an oversized laser beam spot having a spot width, as considered along the scan direction, which is at least two times greater than a minimum element width, the method comprising the steps of:a) detecting light reflected by the oversized beam spot off the elements along the scan direction, and generating an analog signal indicative of the symbol being swept; b) convoluting the analog signal with the oversized beam spot to generate a convoluted signal having peaks and valleys, each peak and valley between adjacent elements of different widths being offset by an edge shift from the edge between the adjacent elements of different widths; c) estimating the edge shift to generate an estimated edge shift; and d) correcting each offset peak and valley by the estimated edge shift to align each offset peak and valley with the edge between the adjacent elements of different widths. 2. The method of claim 1, wherein the estimating step includes estimating a time and an amplitude for each peak and valley of the convoluted signal.3. The method of claim 2, wherein the estimating step includes creating histograms of a time and an amplitude estimated for each peak and valley, and selecting minimum occurrences of times and minimum occurrences of amplitudes as corresponding to an edge between adjacent elements of narrow widths.4. The method of claim 3, wherein the minimum occurrences of times and the minimum occurrences of amplitudes are used to identify sequences of adjacent elements of narrow widths.5. The method of claim 4, wherein the elements adjacent to identified sequences of adjacent elements of narrow widths are identified as elements of wide widths.6. The method of claim 5, wherein the width of elements of narrow width and the estimated edge shift are estimated from the width of elements of the identified sequences of the adjacent elements of narrow widths.7. The method of claim 3, wherein the estimating step includes selecting times that are twice as long as the time of an element of narrow width as identifying an elemet of wide width.8. The method of claim 7, wherein remaining elements are identified as interleaving elements of narrow and wide widths.9. The method of claim 7, wherein the estimating step includes distingishing between the elements of wide and narrow widths.10. The method of claim 1, wherein the correcting step is performed by adding a correction factor equal to the estimated edge shift to a time coordinate of an edge located between an element of wide width followed by an element of narrow width, and by subtracting the correction factor from an edge located between an element of narrow width followed by an element of wide width.